He might just have Relocation Stress. For these igs, a week of fasting is common. Make sure his habitat is located in a stress free area, and is free of looming sight-seers and the gaze of predators like cats ad dogs. The higher on the wall a vivarium is located, the les stress the ig feels. Six feet to the bottom of the habitat is good. OTOH, he needs to at least see people several times per day.
Non eating is a common freak out for owners of recently relocated iguanas.
He can avoid water, but if he's not eating and drinking at night,, you might have to do something. Lack of metabolic water can permanently damage his kidneys.
It's similar with humans - we can go 25 or more days without eating, but only three days without drinking.
Your vet might show you how to make sub-q injections of special water. I've done that before when I was convinced that an ig was not drinking for days at a time. That's a lot better than forcing water by mouth. But the non-water-intake has to stop. My vet used to give me a handful of tuberculin syringes and a container of IV water
I used to put out several small dishes of water so that my ig would find them with very little wandering. A larger bathing container might encourage him to defecate in it. all of my igs would gulp down water as they were climbing in. Once they poop in it, it must be disinfected and replaced. Pan-pooping is boring work, but the ig at least has a higher chance of contacting water.